President Barack Obama and Cuban President Raul Castro on Monday expressed differences over human rights and democracy, but nevertheless confirmed their shared commitment to strengthening ties between the two countries.

The two leaders took turns giving short speeches at a joint press conference in Havana, with Obama hailing the “new day” in bilateral relations.

But the prepared statements were followed by a stunning questions session in which Castro challenged a reporter to present him with a list of names of political prisoners in the Communist-run island.

Asked by US television reporter Jim Acosta about political prisoners in Cuba, Castro seemed oblivious, first saying he couldn't hear the question, then asking whether it was directed at him or Obama.

Eventually he went on the offensive, telling the journalist that if he could offer a list of the alleged prisoners, "they will be released before tonight ends".

"What political prisoners? Give me a name or names," Castro said, later abruptly ending the press conference by explaining he had promised to keep the evening’s programme on schedule.

"I think this is enough," Castro said, throwing up his hands.

Putting Castro on the spot

Questioning by reporters is a routine occurrence for US presidents, but an anomaly in Cuba, where the media are tightly controlled.

Though Castro's answers were far from forthcoming, the mere occurrence of the news conference was seen as significant. During Monday’s press conference Castro often fumbled with his translation headphones, conferred with some of his senior officials seated in the audience, and responded to another US reporter by offering his own rhetorical questions.

Obama and Castro 'getting along' despite differences

It's extremely rare for Raul Castro to preside at a news conference, although he has sometimes taken questions from reporters spontaneously. He's known as a much more cautious and reluctant public speaker than his loquacious older brother Fidel, who was given to talking for hours at a time and often directly with journalists.

There are a handful of independent online outlets, though more critical ones like dissident blogger Yoani Sanchez's 14ymedio are blocked on the island.

Cuba is criticised for briefly detaining demonstrators thousands of times a year but has drastically reduced its practice of handing down long prison sentences for crimes that human rights groups consider to be political.

Cuba released dozens of political prisoners as part of its deal to normalise relations with Cuba, and Amnesty International said in its 2015/2016 report that it knew of no prisoners of conscience in Cuba.

Ending the embargo

Obama said he and Castro had "frank and candid" discussions about human rights as well as areas of cooperation, including in the fields of health, science and the environment.

Castro said much more could be achieved if the United States completely lifted its 54-year-old trade embargo on the island.

Obama also expressed hope that changes he and Castro had set in motion would continue beyond his time in office and said he believed the embargo would eventually end.

He said that while he could not predict when the embargo would be lifted, it would happen because it had failed to serve the interest of the US or the Cuban people for decades.

Obama said his administration had exercised as much flexibility as it could to make modifications to the embargo, but the list of things he could do was growing shorter.

He reminded his Cuban hosts that the bulk of changes related to the embargo relied on Congress.